Document EP 2 565 400 A2 discloses a gas duct for a gas turbine, which gas duct is formed by a concentric inner casing and an outer casing which concentrically encompasses the inner casing at a distance, and through which the exhaust gases from the gas turbine discharge to the outside. The inner casing and the outer casing are interconnected by means of a multiplicity of radial support struts. The support struts, the outer casing and the inner casing are equipped in each case with a heat-resistant lining for protection against the hot exhaust gases. Easy accessibility and an extensive reduction of thermal stresses is achieved by the linings of the support struts of the outer casing and of the inner casing being divided in each case into a plurality of separate segments which are fastened on a support structure in such a way that an individual thermal expansion of the individual segments is possible.
However, for the fixation of the segments, carrier beams are used. These carrier beams and a specific “star” form of inner/outer flanges are exposed to high temperatures and stresses in steady state, and therefore certain criteria of Low Cycle Fatigue (LCF) and creep of the support structure are failed.
Furthermore, connection bolts are exposed to the main gas flow. A high temperature of the bolts and connected parts and temperature gradients in both transient and steady state could lead to creep of bolt material and consequently to the loss of bolt's pretension.